PHOTOBLEACHING ACTIVITY OF 2-(PHENYLAMINO)METHYLIDENECYCLOHEXANE-1,3-DIONES IN TOBACCO (NICOTIANA-TABACUM) CULTURED-CELLS

A series of phenylalkylidenecyclohexane-1,3-dione derivatives were des igned and synthesized as vinylogous analogs of phthalimides, which are known photobleaching herbicides. The bleaching activity of synthesize d compounds was assayed with photomixotrophic tobacco cultured cells u nder either light or dark conditions. Both the chlorophyll and the car otenoid contents of the cells treated with the cyclic diones decreased to almost zero within 24 h under the light condition but not under th e dark condition. This rapid emergence of bleaching activity with ligh t is one of the most distinctive actions of Protox-inhibiting herbicid es; however, the cyclic dione did not inhibit protoporphyrinogen oxida se in vitro. Thus, we concluded that the cyclic diones possessed a dif ferent herbicidal mode of action from Protox-inhibiting herbicide.